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JDK1.8 Stream
1.Streams filter() and collect() 进行过滤数据和收集数据
按照正常的方式过滤数据
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ist<String> lines = Arrays.asList(
"spring"
,
"node"
,
"mkyong"
);
List<String> result = getFilterOutput(lines,
"mkyong"
);
for
(String temp : result) {
System.out.println(temp);
//output : spring node
}
//...
private
static
List<String> getFilterOutput(List<String> lines, String filter) {
List<String> result =
new
ArrayList<>();
for
(String line : lines) {
if
(!
"mkyong"
.equals(line)) {
result.add(line);
}
}
return
result;
}
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JDK1.8之后过滤数据的方式
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import
java.util.stream.Collectors;
//...
List<String> lines = Arrays.asList(
"spring"
,
"node"
,
"mkyong"
);
List<String> result = lines.stream()
//convert list to stream
.filter(line -> !
"mkyong"
. equals (line))
//filters the line, equals to "mkyong"
.collect(Collectors.toList());
//collect the output and convert streams to a List
result.forEach(System.out::println);
//output : spring node
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2. Streams filter(), findAny() and orElse()
按照正常方式,通过名字获取对象
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ist<Person> persons = Arrays.asList(
new
Person(
"mkyong"
),
new
Person(
"michael"
),
new
Person(
"lawrence"
));
Person result = getStudentByName(persons,
"michael"
);
//...
private
Person getStudentByName(List<Person> persons, String name) {
Person result =
null
;
for
(Person temp : persons) {
if
(name.equals(temp.getName())) {
result = temp;
}
}
return
result;
}
|
使用stream.filter ()过滤一列表，并.findAny().orElse (null)返回一个对象的条件。
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List<Person> persons = Arrays.asList(
new
Person(
"mkyong"
),
new
Person(
"michael"
),
new
Person(
"lawrence"
));
Person result = persons.stream()
// Convert to steam
.filter(x ->
"michael"
.equals(x.getName()))
// we want "michael" only
.findAny()
// If 'findAny' then return found
.orElse(
null
);
// If not found, return null
|
更多赛选条件
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List<Person> persons = Arrays.asList(
new
Person(
"mkyong"
,
20
),
new
Person(
"michael"
,
21
),
new
Person(
"lawrence"
,
23
));
Person result = persons.stream()
.filter((x) ->
"michael"
.equals(x.getName()) &&
21
==x.getAge())
.findAny()
.orElse(
null
);
//or like this
Person result = persons.stream()
.filter(x -> {
if
(
"michael"
.equals(x.getName()) &&
21
==x.getAge()){
return
true
;
}
return
false
;
}).findAny()
.orElse(
null
);
|
使用filter和map例子
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List<Person> persons = Arrays.asList(
new
Person(
"mkyong"
,
20
),
new
Person(
"michael"
,
21
),
new
Person(
"lawrence"
,
23
));
String name = persons.stream()
.filter(x ->
"michael"
.equals(x.getName()))
.map(Person::getName)
//convert stream to String
.findAny()
.orElse(
""
);
//name = michael
|
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<div class="postDesc">posted @ <span id="post-date">2016-09-08 10:27</span> <a href="https://www.cnblogs.com/julian-keen/">重新的开始</a> 阅读(<span id="post_view_count">4212</span>) 评论(<span id="post_comment_count">0</span>) <a href="https://i.cnblogs.com/EditPosts.aspx?postid=5852004" rel="nofollow">编辑</a> <a href="#" onclick="AddToWz(5852004);return false;">收藏</a></div>
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